This invention relates to oscillator circuits in general and particularly to Ga As FET (Gallium Arscenide Field Effect Transistor) oscillators. The use of a Ga As FET in an oscillators circuit can present problems relating to noise generation and loading of the tank circuit. These problems occur due to the relatively low forward bias voltage across the gate-source junction of the transistor required for the gate-source current flow. For a Ga As FET this voltage is approximately 0.2 volts as the gate-source junction of Ga As FET device is essentially a Schottky diode. When the signal applied across the gate-source junction exceeds the 0.2. volts, gate-source current flows, which both loads the oscillator tank circuit, as well as introduces noise in the oscillator output.
In JFET (junction field effect transistor) oscillator circuits, it is well known to provide a silicon diode from gate to ground ot limit the gate-source voltage. This approach limits the gate to ground voltage to approximately 0.6 volts, the forward bias voltage drop of the diode. It is also known to use a Schottky diode directly across a JFET gate-source connection, and from gate to ground (that is AC and DC ground). These approaches are not practical for use in Ga As FET oscillator circuits as gate-source current can flow under any of the arrangements.